package com.leo.util;


import java.io.ByteArrayOutputStream;  
import java.io.IOException;  
import java.io.OutputStream; 

public class Base64 { 
	
	 	private static final char[] legalChars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/".toCharArray();  
	    /** 
	     * data[]进行编码 
	     * @param data 
	     * @return 
	     */  
	        public static String encode(byte[] data) {  
	            int start = 0;  
	            int len = data.length;  
	            StringBuffer buf = new StringBuffer(data.length * 3 / 2);  
	  
	            int end = len - 3;  
	            int i = start;  
	            int n = 0;  
	  
	            while (i <= end) {  
	                int d = ((((int) data[i]) & 0x0ff) << 16)  
	                        | ((((int) data[i + 1]) & 0x0ff) << 8)  
	                        | (((int) data[i + 2]) & 0x0ff);  
	  
	                buf.append(legalChars[(d >> 18) & 63]);  
	                buf.append(legalChars[(d >> 12) & 63]);  
	                buf.append(legalChars[(d >> 6) & 63]);  
	                buf.append(legalChars[d & 63]);  
	  
	                i += 3;  
	  
	                if (n++ >= 14) {  
	                    n = 0;  
	                    buf.append(" ");  
	                }  
	            }  
	  
	            if (i == start + len - 2) {  
	                int d = ((((int) data[i]) & 0x0ff) << 16)  
	                        | ((((int) data[i + 1]) & 255) << 8);  
	  
	                buf.append(legalChars[(d >> 18) & 63]);  
	                buf.append(legalChars[(d >> 12) & 63]);  
	                buf.append(legalChars[(d >> 6) & 63]);  
	                buf.append("=");  
	            } else if (i == start + len - 1) {  
	                int d = (((int) data[i]) & 0x0ff) << 16;  
	  
	                buf.append(legalChars[(d >> 18) & 63]);  
	                buf.append(legalChars[(d >> 12) & 63]);  
	                buf.append("==");  
	            }  
	  
	            return buf.toString();  
	        }  
	  
	        private static int decode(char c) {  
	            if (c >= 'A' && c <= 'Z')  
	                return ((int) c) - 65;  
	            else if (c >= 'a' && c <= 'z')  
	                return ((int) c) - 97 + 26;  
	            else if (c >= '0' && c <= '9')  
	                return ((int) c) - 48 + 26 + 26;  
	            else  
	                switch (c) {  
	                case '+':  
	                    return 62;  
	                case '/':  
	                    return 63;  
	                case '=':  
	                    return 0;  
	                default:  
	                    throw new RuntimeException("unexpected code: " + c);  
	                }  
	        }  
	  
	        /** 
	         * Decodes the given Base64 encoded String to a new byte array. The byte 
	         * array holding the decoded data is returned. 
	         */  
	  
	        public static byte[] decode(String s) {  
	  
	            ByteArrayOutputStream bos = new ByteArrayOutputStream();  
	            try {  
	                decode(s, bos);  
	            } catch (IOException e) {  
	                throw new RuntimeException();  
	            }  
	            byte[] decodedBytes = bos.toByteArray();  
	            try {  
	                bos.close();  
	                bos = null;  
	            } catch (IOException ex) {  
	                System.err.println("Error while decoding BASE64: " + ex.toString());  
	            }  
	            return decodedBytes;  
	        }  
	  
	        private static void decode(String s, OutputStream os) throws IOException {  
	            int i = 0;  
	  
	            int len = s.length();  
	  
	            while (true) {  
	                while (i < len && s.charAt(i) <= ' ')  
	                    i++;  
	  
	                if (i == len)  
	                    break;  
	  
	                int tri = (decode(s.charAt(i)) << 18)  
	                        + (decode(s.charAt(i + 1)) << 12)  
	                        + (decode(s.charAt(i + 2)) << 6)  
	                        + (decode(s.charAt(i + 3)));  
	  
	                os.write((tri >> 16) & 255);  
	                if (s.charAt(i + 2) == '=')  
	                    break;  
	                os.write((tri >> 8) & 255);  
	                if (s.charAt(i + 3) == '=')  
	                    break;  
	                os.write(tri & 255);  
	  
	                i += 4;  
	            }  
	        }  

          
}  

